Do Red Blood Cells have a nucleus? 11 facts that you should know

  Red Blood cells are also known as erythrocytes and are indulged in the function of carrying fresh oxygen across various parts of the body. They are round in shape and have haemoglobin which provides the red colour. 

Do all red blood cells have a nucleus?

Unlike the other cells in our body, the red blood cells do not have a nucleus. In some of the vertebrates like the birds, reptiles or fish, there are traces of nucleus but in the inactive form. This is mostly due to evolution that the red blood cells in the mammals lack red blood cells. 

Do mature red blood cells have a nucleus?

Mature red blood cells lack a nucleus. The red blood cells which are produced in the bone marrow of the organisms tend to initially have a nucleus. In the maturation phase, these red blood cells undergo the process of enucleation where the nucleus is extruded. Hence, the mature red blood cells that enter the blood circulation process lack any form of nucleus. 

Do human red blood cells have a nucleus?

Humans fall under the category of mammals and are identified as the most evolved form of life on earth and hence lacks a nucleus in their mature set of red blood cells in order to support their functioning in a better manner.  

do red blood cells have a nucleus
Red Blood Cells from Wikimedia

Do animal red blood cells have a nucleus?

In most of the animals like the fish or amphibians or reptiles or birds tend to contain nuclei which even have a DNA. The exceptionals are the mammals which do not contain any nucleus in the red blood cells.

In certain exceptional cases within mammals like in dogs, cats or camelids, nucleated red blood cells can be observed when they are suffering from strongly regenerative anaemia. Camelids with any other conditions of illness can also portray nucleated red blood cells. 

Why do animal red blood cells have a nucleus?


Animals like the birds have been identified to have nucleus in the red blood cells which helps in establishing a better homeostasis. 

The nucleated RBCs help in utilising water in a better manner and have the ability to multiply using the process mitosis. This is helpful in surviving the osmotic stress by the birds. 


The nucleated red blood cells within the fish help in increasing the overall level of oxygen availability at the cellular level. This ensures effective breathing under the water where oxygen availability is comparatively limited. 

Do frog red blood cells have a nucleus?

Amphibians, like frogs, have been identified to have flattened and elliptical shaped red blood cells which appear to be biconvex from its edges. The red blood cells of frogs are filled with straw colour cytoplasm and have a round definite nucleus at the centre. 

Why does frog RBC have a nucleus?

Denucleation is the process which was established in mammals to increase the capacity of gas exchange in order to support the endotherms with metabolic support. The RBCs without nucleus support greater ability to meet demand with increased space for haemoglobin. Frogs are ectotherms and hence, the metabolic rate is lower with lesser demand for gas exchange capacity. Thus, the nucleus is not excluded. 

Do mammalian red blood cells have a nucleus?

Mammals are exceptional in the animal kingdom and do not have a nucleus in the red blood cells. The RBCs lack both mitochondria and nucleus to increase space for haemoglobin. 

Why do red blood cells not have a nucleus?

The lack of nucleus in the red blood cells in mammals can be identified as an adaptation in order to facilitate betterment in the task of RBCs in the body, that is to carry greater amounts of oxygen to be circulated in the body. 

As the red blood cells enter the bloodstream, the nucleus is ejected out along with other organelles. The removal of the nucleus from the RBCs helps to carry more haemoglobin which allows greater space for more oxygen. 

The removal of nucleus also helps in increasing the flexibility of the red blood cells in order to help them move through capillaries which are half the overall sizes of the cells. 

What can red blood cells not do without a nucleus?

The lack of nucleus has led the red blood cells to have a very limited lifespan. The average lifespan of a red blood cell is 120 days. 

The red blood cells require a large amount of energy to support the travelling through the blood vessels to distribute blood across various parts of the body. The lack of nucleus leads to the lack of supply of energy.  

How do red blood cells survive without a nucleus?

The red blood cells tend to survive without a nucleus but only for a limited set of days, which in average is 120 days. After this, all the energy gets exhausted due to the travelling to various parts of the body to provide oxygen, causing the cells to die. 

Advantages of red blood cells not having a nucleus?

There are various advantages of red blood cells in not having a nucleus. One is it allows the easy passage of the cells through the narrow capillaries which are half the sizes of the cells. 

Another one is the greater space in the cells for haemoglobin which allows greater ability to take oxygen and circulate across the mammalian body to meet the high metabolic needs. 

Disadvantage of red blood cells not having a nucleus?

The disadvantage of the red blood cells not having a nucleus would include a lower life span which is around 120 days.


In conclusion, it has been identified that there is no nucleus in the Red Blood Cells of the mammals but there is the presence of nucleus in amphibians, fishes and reptiles.

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